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During the COVID-19 pandemic, delays increased due to COVID prioritization and reluctance to seek care. A 70-year-old man was initially misdiagnosed with COVID-19; persistent symptoms led to imaging findings and surgical resection, with histopathology confirming medullary carcinoma and metastatic spread supported by immunohistochemistry. The case emphasizes maintaining robust diagnostic pathways and improving techniques such as immunohistochemistry.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/diagnostic-challenges-of-medullary-carcinoma-of-the-small-intestine-during-the-covid-19-pandemic/371220/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/diagnostic-challenges-of-medullary-carcinoma-of-the-small-intestine-during-the-covid-19-pandemic/371220.png","ImageObject",300,407,{"name":92,"@type":93},"Olivia Brown","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-29","2026-09-23",true,{"@type":102,"interactionType":103,"userInteractionCount":34},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"Why is diagnosis of medullary carcinoma of the small intestine especially challenging?","Question",{"text":112,"@type":113},"It is exceptionally rare and shows a solid growth pattern without glandular structures, with histopathological features that resemble other poorly differentiated tumors, leading to diagnostic delays.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How did the COVID-19 pandemic affect the diagnostic timeline in the case described?",{"text":117,"@type":113},"Diagnostic delays became more common as COVID-related cases were prioritized and patients were reluctant to seek medical attention, contributing to delayed identification of the cancer.",{"name":119,"@type":110,"acceptedAnswer":120},"What investigations supported the final diagnosis in the case?",{"text":121,"@type":113},"Imaging revealed focal lesions and thickened small intestinal walls, while histopathology and immunohistochemistry confirmed medullary carcinoma using positive markers and excluding other malignancies.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},371220,1790390791,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":34,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":52,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144},16904993612988,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","Article  \nDiagnostic Challenges of Medullary Carcinoma of the Small Intestine During the COVID-19 Pandemic  \nDanuta Szkudlarek 1, Katarzyna Skórkowska-Telichowska 2,3 and Benita Wiatrak 4, *  \nAcademic Editor: Maximos Frountzas  \nReceived: 19 November 2024  \nRevised: 21 December 2024  \nAccepted: 31 December 2024  \nPublished: 7 January 2025  \nCitation: Szkudlarek, D.; Skórkowska-Telichowska, K.; Wiatrak, B. Diagnostic Challenges of Medullary Carcinoma of the Small Intestine During the COVID-19 Pandemic. J. Clin. Med. 2025, 14, 298. [https://](https://)[ ](https://)[doi.org/10.3390/jcm14020298](doi.org/10.3390/jcm14020298)  \n[Copyright:](Copyright:) © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([https://creativecommons.org/](https://creativecommons.org/)[ ](https://creativecommons.org/)[licenses/by/4.0/](licenses/by/4.0/)) .  \n1 Pathology Department, Provincial Hospital Center of the Jelenia Góra Valley, 58-506 Jelenia Góra, Poland  \n2 Department of Non-Surgical Clinical Sciences, Faculty of Medicine, Wrocław University of Science and Technology, Wybrzez˙ e Wyspia ´nskiego 27, 50-370 Wrocław, Poland  \n3 Department of Endocrinology, Jerzy Gromkowski Regional Specialist Hospital, Koszarowa 5 Str., 51-149 Wrocław, Poland  \n4 Department of Pharmacology, Faculty of Medicine, Wrocław Medical University, 50-345 Wrocław, Poland  \n* [Correspondence: benita.wiatrak@umw.edu.pl](Correspondence: benita.wiatrak@umw.edu.pl)  \nAbstract: Background: Medullary carcinoma of the small intestine is an exceptionally rare subtype of gastrointestinal cancer, characterized by its solid growth pattern and lack of glandular structures, which complicate timely diagnosis. During the COVID-19 pandemic, diagnostic delays for rare cancers became increasingly common due to the prioritization of COVID-related cases and patient reluctance to seek medical attention. Methods and Result: We present the case of a 70-year-old male initially misdiagnosed with COVID-19, whose persistent symptoms led to the eventual discovery of medullary carcinoma. Imaging studies revealed focal lesions in the liver, spleen, and thickened small intestinal walls, prompting surgical resection of a 16 cm intestinal segment. Histopathological examination confirmed medullary carcinoma with lymph node and liver metastases, supported by immunohistochemistry, which showed positive markers (calretinin, pancytokeratin, cytokeratin 7) and excluded other malignancies. Conclusions: The diagnostic delay, exacerbated by the pandemic, highlights the challenges of distinguishing rare cancers from more common conditions during global health crises. This case underscores the importance of advanced diagnostic techniques, such as immunohistochemistry, for accurate identification. Maintaining robust cancer diagnostic pathways during emergencies is crucial to avoid delays in treatment. Future research should focus on improving screening methods for rare cancers and developing resilient healthcare systems to mitigate similar challenges in future crises.  \nKeywords: medullary carcinoma; small intestine neoplasm; COVID-19 diagnostic challenges; gastrointestinal cancer; immunohistochemistry; calretinin; rare cancer diagnosis  \n1. Introduction  \nRare cancers represent a unique and exceptionally challenging domain in medicine, both in diagnostics and treatment. These malignancies, defined as affecting fewer than six individuals per 100,000 annually, pose distinctive hurdles due to limited clinical knowledge, nonspecific symptoms, and often scarce diagnostic and therapeutic guidelines. Within this category, small intestine cancers account for less than 5% of all gastrointestinal cancers, making them an uncommon but diagnostically complex group of malignancies [1,2] . Medullary carcinoma of the small intestine (MC-SI) is an exceedingly rare subtype, characterized by its so","cbCaim3Y1LPpvzG1","https://ap.wps.com/l/cbCaim3Y1LPpvzG1","pdf",1412703,"English","# Abstract\n# Introduction","[{\"question\":\"Why is diagnosis of medullary carcinoma of the small intestine especially challenging?\",\"answer\":\"It is exceptionally rare and shows a solid growth pattern without glandular structures, with histopathological features that resemble other poorly differentiated tumors, leading to diagnostic delays.\"},{\"question\":\"How did the COVID-19 pandemic affect the diagnostic timeline in the case described?\",\"answer\":\"Diagnostic delays became more common as COVID-related cases were prioritized and patients were reluctant to seek medical attention, contributing to delayed identification of the cancer.\"},{\"question\":\"What investigations supported the final diagnosis in the case?\",\"answer\":\"Imaging revealed focal lesions and thickened small intestinal walls, while histopathology and immunohistochemistry confirmed medullary carcinoma using positive markers and excluding other malignancies.\"}]","Diagnostic Challenges of Medullary Carcinoma of the Small Intestine During the COVID-19 Pandemic | PDF",1790191548,25]